1. Field of the Invention
The present invention relates to a transparent electrode and a preparation method thereof. More specifically, the present invention relates to a transparent electrode comprising a grid electrode and a conductive polymer layer with a nano-metal layer interposed therebetween on a transparent substrate, where the transparent electrode exhibits high optical transmittance and low resistance and can be produced at low production cost, and a preparation method thereof.
2. Description of the Related Art
An electrode, which is generally constructed of a transparent conductive film formed on a transparent substrate, is used in a broad variety of devices requiring light transmission and electroconductivity, including image sensors, fuel cells, liquid crystal displays, organic electroluminescent (“EL”) displays, touch screen panels, and the like.
With the commercialization of digital broadcasting, high-resolution large displays, of which flat displays, such as liquid crystal displays (“LCDs”) and plasma display panels (“PDPs”), are representative, have been in great demand and have been popularized. Recently, a digital multimedia broadcasting (“DMB”) service, which is a digital radio transmission system for sending multimedia (radio, TV and datacasting) to mobile devices such as mobile phones, and which can operate via satellite (“S-DMB”) or terrestrial (“T-DMB”) transmission, has been introduced. In addition, ubiquitous computing is now possible. Under these circumstances, increasing attention has been paid to flexible displays, which are now regarded as the next-generation display to succeed thin film transistor LCD (“TFT-LCD”), PDP and organic EL displays.
Flexible displays may be realized based on the principles of conventional displays with the modification that a glass substrate is replaced with a flexible substrate, or a switching device is replaced with the organic semiconductor organic thin film transistor (“OTFT”). Alternatively, flexible displays may be embodied as e-paper, microcapsule electrophoretic displays, and twist-ball displays.
In various displays including flexible displays, indium tin oxide (“ITO”) electrodes have predominated over other electrodes due to the ability of ITO to be formed into a thin film on glass substrates and to the excellent light transmittance and electroconductivity of the ITO. For the preparation of ITO electrodes, a vacuum evaporation apparatus is generally used to deposit the ITO. Most vacuum evaporation apparatuses employ a sputtering process. When used to prepare a transparent electrode, a sputtering process can use a temperature of 200° C. and, in extreme cases, as high as 400° C. However, silicon substrates of transparent electrodes for LCDs or image sensors may not be able to endure such high temperatures. Specifically, the preparation of flexible displays cannot be conducted at such high processing temperatures, as such temperatures can cause the display substrate to deform. In addition, ITO electrodes suffer from the disadvantage of decreased durability when applied to flexible displays.